Flame retardant adhesive composition, and adhesive sheet, coverlay film and flexible copper-clad laminate using same

Abstract

Provided is a flame retardant adhesive composition including (A) a halogen-free epoxy resin, (B) a thermoplastic resin and/or a synthetic rubber, (C) a curing agent, (D) an organophosphinate compound, (E) a curing accelerator, and (F) a nitrogen-containing organophosphate compound represented by a general formula (1) shown below: (wherein, R 1 to R 4 each represent a hydrogen atom or an alkyl group, and X represents a nitrogen-containing bivalent organic group) Also provided are an adhesive sheet having a layer comprising the above composition, and a protective layer for covering the layer comprising the composition; a coverlay film having an electrically insulating film, and a layer comprising the above composition provided on top of the film; and a flexible copper-clad laminate having an electrically insulating film, a layer comprising the above composition provided on top of the film, and a copper foil provided on top of the layer comprising the composition. Further provided are a process for producing the adhesive sheet, a process for producing the coverlay film, and a process for producing the flexible copper-clad laminate. The halogen-free adhesive composition yields a cured product, on curing, that exhibits excellent flame retardancy and electrical characteristics (anti-migration properties). The composition can be used for producing an adhesive sheet, a coverlay film, and a flexible copper-clad laminate.

1 . A flame retardant adhesive composition comprising 
 (A) a halogen-free epoxy resin,    (B) a thermoplastic resin and/or a synthetic rubber,    (C) a curing agent,    (D) an organophosphinate compound,    (E) a curing accelerator, and    (F) a nitrogen-containing organophosphate compound represented by a general formula (1) shown below:                          (wherein, R 1 , R 2 , R 3 , and R 4  each represent, independently, a hydrogen atom or an alkyl group, and X represents a bivalent organic group that comprises a nitrogen atom).    
     
     
         2 . The flame retardant adhesive composition according to  claim 1 , wherein said component (B) is at least one polymer compound selected from the group consisting of polyester resins, acrylic resins, phenoxy resins, and carboxyl group-containing acrylonitrile butadiene rubbers.  
     
     
         3 . The flame retardant adhesive composition according to  claim 1 , wherein said component (D) is an organophosphinate salt represented by a general formula (2) shown below:  
       
         
           
           
               
               
           
         
       
       (wherein, R 5  and R 6  each represent, independently, an unsubstituted or substituted monovalent hydrocarbon group, M represents an alkali metal, alkaline earth metal, transition metal, or typical element from group 14 of the periodic table, and m represents an integer from 1 to 4).  
     
     
         4 . The flame retardant adhesive composition according to  claim 1 , wherein said component (D) is an aluminum organophosphinate.  
     
     
         5 . The flame retardant adhesive composition according to  claim 1 , wherein the phosphorus content within said component (D) is within a range from 15 to 30% by mass, relative to the mass of said component (D).  
     
     
         6 . The flame retardant adhesive composition according to  claim 1 , wherein the blend quantity of the component (D) is within a range from 0.1 to 15 parts by mass, relative to 100 parts by mass of the combination of said components (A) through (F).  
     
     
         7 . The flame retardant adhesive composition according to  claim 1 , wherein said component (F) is an aromatic piperazine phosphate represented by a general formula (3) shown below:  
       
         
           
           
               
               
           
         
       
       (wherein, R 1 , R 2 , R 3 , and R 4  are as defined above).  
     
     
         8 . The flame retardant adhesive composition according to  claim 1 , wherein said component (F) is the compound shown below:  
       
         
           
           
               
               
           
         
       
     
     
         9 . The flame retardant adhesive composition according to  claim 1 , wherein the blend quantity of the component (F) is within a range from 1 to 13 parts by mass, relative to 100 parts by mass of said adhesive composition.  
     
     
         10 . An adhesive sheet, having a layer comprising the composition defined in  claim 1 , and a protective layer for covering said layer comprising said composition.  
     
     
         11 . A coverlay film, having an electrically insulating film, and a layer comprising the composition defined in  claim 1  provided on top of said film.  
     
     
         12 . The coverlay film according to  claim 11 , wherein said electrically insulating film is a polyimide film.  
     
     
         13 . A flexible copper-clad laminate, having an electrically insulating film, a layer comprising the composition defined in  claim 1  provided on top of said film, and a copper foil provided on top of said layer comprising said composition.  
     
     
         14 . The flexible copper-clad laminate according to  claim 13 , wherein said electrically insulating film is a polyimide film.  
     
     
         15 . A process for producing an adhesive sheet, having a layer comprising the composition defined in  claim 1 , and a protective layer for covering said layer comprising said composition, said process comprising the steps of: 
 applying to a protective layer a dispersion comprising said composition and an organic solvent,    removing said organic solvent to dry said composition, thereby forming a layer comprising said composition, and    crimping and laminating said layer comprising said composition to another protective layer, thereby forming said adhesive sheet.    
     
     
         16 . A process for producing a coverlay film, having an electrically insulating film, and a layer comprising the composition defined in  claim 1  provided on top of said film, said process comprising the steps of: 
 applying to an electrically insulating film a dispersion comprising said composition and an organic solvent, and    removing said organic solvent to dry said composition and to form a layer comprising said composition, thereby forming said coverlay film.    
     
     
         17 . A process for producing a flexible copper-clad laminate, having an electrically insulating film, a layer comprising the composition defined in  claim 1  provided on top of said film, and copper foil provided on top of said layer comprising said composition, said process comprising the steps of: 
 applying to an electrically insulating film a dispersion comprising said composition and an organic solvent,    removing said organic solvent to dry said composition, thereby forming a layer comprising said composition, and    laminating said layer comprising said composition to a copper foil, thereby forming said flexible copper-clad laminate.